1. Field of the Invention
The present invention relates to a switch driving circuit.
2. Description of Related Art
Conventionally, a switch driving circuit, which complementarily turns on/off a first switch and a second switch connected in series between two different electric potential points, has a dead time (concurrent turning-on prevention period) for turning off both switches as a purpose for preventing a through-current when switching on/off states of each switch (e.g., see JP-A-2010-178437).
Besides, conventionally, also an output driver circuit, which can adjust a slew rate of a gate signal for turning on/off a switch, is disclosed (e.g., see JP-A-2006-325256).
Because an electric current flows in a body diode parasitic in a switch (MOSFET [metal oxide semiconductor field effect transistor] and IGBT [insulated gate bipolar transistor]) during the dead time, power loss caused by a forward drop voltage occurs. Accordingly, in light of efficiency increase (power consumption reduction), it is desirable that the dead time is as short as possible. However, if the dead time is set too short, the first switch and the second switch become likely to be easily turned on concurrently; there is a high risk that a through-current occurs. Because of this, it becomes important to set the dead time at an appropriate length considering both efficiency increase and safety securing.
In the meantime, the shortest possible dead time necessary for preventing the through-current changes depending on various circuit conditions (slew rate, input voltage and the like). However, in the conventional switch driving circuit, the dead time is set fixedly under a circuit condition expected in advance. Because of this, there is a risk that if the circuit condition changes, the dead time becomes unnecessarily long or short.